Published German Application 43 17 578 discloses a method of reprocessing zinc- and lead-containing residual materials from metallurgical plants. In that method, zinc- and lead-containing residual materials from metallurgical plants are reprocessed by a thermal treatment in a circulating fluidized bed system. The required heat is supplied in that solid carbon is combusted in the fluidized bed reactor of the circulating fluidized bed system. A solid carbon content from 5 to 30% is adjusted in the lower portion of the fluidized bed. Oxygen-containing gases are supplied to the upper portion of the fluidized bed reactor, and the formation of CO.sub.2 is so restricted that zinc metal is not oxidized. The suspension which has been discharged is treated in a recycle cyclone to remove substantially all solids, which are then recycled. The gas is cooled to a temperature at which zinc metal is oxidized to ZnO. The dustlike compounds of zinc and lead are separated from the gas.
In the known method, up to 85% by weight of the zinc contained in the iron oxide-containing residual material are volatilized. For this reason 0.15% by weight zinc is still contained in the reprocessed iron oxide-containing residual material. In the succeeding blast furnace process that zinc content is disturbing because it gives rise to a circulation of zinc, caking, and higher costs.